Iceotope's immersively cooled server racks are now in production, and the company has named its first customer. The University of Leeds, has been using an Iceotope server since December to run computational fluid dynamics models -- and to warm the radiators in one of its laboratories.
The company showed off prototypes of its unusual liquid-cooled system at the Cebit trade show in Germany last March, but took another few months to figure out how to mass-produce the aluminum server modules, which are filled with Novec, an inert coolant liquid from 3M.
The Novec carries heat from the server motherboard to the module's surface by natural convection, without the need for noisy, inefficient fans. Water is pumped to the top of the rack, from where it trickles down over the modules to a heat exchanger. A secondary water circuit then carries the heat away, either to a rooftop cooling system or, at the University of Leeds, to regular domestic radiators.
The many fans in a typical server rack might be turning as much as 6kW of electricity into acoustic and thermal energy as they push air around, according to senior lecturer Jon Summers. Iceotope's racks are cooled by two 40W water pumps, and just one could do the job if the other failed, according to company CTO Peter Hopton.
While many data centers are struggling because their servers are running too hot, Summers said that if anything the university's Iceotope server is too cool.
"We're looking at a water temperature of 50 to 55 C from the back of the system going into the radiators, which are normally expecting 70 C," he said. That means each radiator's heat output is around 1.7kW, well below the 2.5kW they would deliver if connected to a central heating system.
A PhD student sponsored by Iceotope is using the server to model how it could be made to run hotter, boosting cooling efficiency -- and warming the laboratory more effectively through the winter, said Summers.
"We are trying to understand what flow rates we need to operate it at and the external circuit that best matches the performance of the system. We've been running some heavy computational loads to generate that heat," he said.
The server is probably worked harder than those in many data centers, he said, because it operates at about 95 percent utilization, running calculations in batch mode for student projects, while utilization in commercial environments is much lower.
The Leeds server has a mix of modules containing both AMD and Intel processors, reflecting the academic interest in experimentation. It has a total of 240 cores and 360GB of RAM.
Processor modules containing two Intel six-core Romley E5-2620 processors, 64Gbytes of RAM and SSD storage start at £3,195. A rack can hold 48 modules, along with dual heat exchangers and dual power supplies for redundancy.
With the servers bathed in fluid and sealed in aluminum boxes, the upgrade options are limited to swapping a box out of the cabinet and putting a new one in.
"Refilling is possible, but nobody has requested it yet," said Iceotope CEO Neil Bennett. "We are encouraging customers to put a lot of memory in from day one. It's not something a customer can just put a new DIMM in."